The chemical and physical processes which proceed during the washing operation continue to be the subject of intensive research because of their complexity.
In all cases wetting of the goods to be cleaned with the wash liquor and phase inversion of the solid or oily particles of dirt is necessary for cleaning. Wetting and phase inversion are effected by surface-active substances, the surfactants. The electrochemical double layer formed between the fibre, dirt particles and surfactant is increased substantially by anionic surfactants and builders, as a result of which the repellency between the dirt and fibre is intensified.
The liquid grease and oil dirt detached is solubilized by the micelles formed by the surfactants and is thus held in the wash liquor. Particles of dirt are charged electrically by adsorption of surfactants and are dispersed in the wash liquor as a consequence of the repellency of the individual particles, so that no redeposition on the fabric takes place.
Nonionic surfactants are in general employed in detergent formulations because of their ability to remove greasy and oily dirt. According to the prior art, cationic surfactants are likewise used in detergent formulations, in particular also because of the additional textile care effects attributed to them, and not exclusively as cleaning agents. Such additional effects which are to be observed, depending on the structure of the cationic surfactants, are, for example, the softening (U.S. Pat. No. 3,607,763), the antistatic (U.S. Pat. No. 3,951,879; U.S. Pat. No. 3,959,157), the bactericidal (U.S. Pat. No. 2,742,434; U.S. Pat. No. 3,539,520; U.S. Pat. No. 3,965,026) and the colour-protecting action or also the improvement in the water uptake capacity of the fabric treated with them. Detergent formulations formulated with a basic pH in which selected nonionic and cationic surfactants are combined in order to achieve an improved removal of dirt are furthermore known, as described in the patents U.S. Pat. No. 4,239,660 or also U.S. Pat. No. 4,260,529.
U.S. Pat. No. 4,260,529 describes, for example, detergent formulations which comprise, in addition to a biodegradable nonionic surfactant, betaine ester derivatives in the form of cationic ammonium salts. These detergent formulations for the main washing operation are attributed a high washing action if they are employed in the main washing operation in an alkaline pH range of expressly below 11, so that hydrolysis of the surfactants employed is prevented.
Cationic surfactants of varying structure are employed as raw materials for rinse cycle fabric softeners. Ester compounds based on triethanolamine, such as N-methyl-, N,N-bis(beta-C14-18-acyloxy-ethyl)-, N-beta-hydroxyethylammonium methosulfate, which are marketed under trade names such as Tetranyl® AT 75 (trademark of KAO Corp.), Stepanex® VRH 90 (trademark of Stepan Corp.) or Rewoquat® WE 18 (trademark of Goldschmidt Rewo GmbH & Co. KG), are particularly widely used.
U.S. Pat. No. 4,370,272 describes alkoxylated quaternary ammonium betaine ester surfactants and their use as hair conditioner or rinse cycle softener. Their self-emulsifying action in water and the possibility of omitting additional nonionic surfactants to achieve a stable emulsion are mentioned as advantages. However, the soft handle of laundry treated with such rinse cycle softeners does not meet the standards achieved by modern esterquat rinse cycle softeners.
A disadvantage of the prior art is furthermore that the surfactant molecules hitherto available have no or an inadequate substantivity in order to be adsorbed on to the fibres from the aqueous liquor, which applies in particular to nonionic surfactant molecules.